1. Field of the Invention
The present application generally relates to a circuit testing interface and test method, and more particularly, to a testing interface of an off-chip driver (OCD) and test method.
2. Description of Related Art
FIG. 1 shows a circuit diagram of a conventional off-chip driver (OCD) and an input buffer. Referring to FIG. 1, the output terminal of the OCD 110 is coupled to a through-silicon via (TSV) 130. An input terminal of the input buffer 120 is coupled to the TSV 130 and the output terminal of the OCD 110.
Traditionally, when the OCD 110 and/or the input buffer 120 are tested, the TSV 130 has to be directly contacted by using a probe on a probe card, and electrical test signals have to be transmitted and received through the TSV 130. In functional mode, the chip OCD 110 is typically attached to other electrical components through the TSV 130. The TSV 130 typically has a relatively low maximum pin capacitance specification. However, since the surface area of a TSV 130 is relatively small, conventional test probes are not configured to reliably probe it. In order to remedy this, one might attach a conventional test pad to the TSV 130 with an on-die metal trace. This attached test probe pad would not typically be used in functional mode because the test probe pad typically has a relatively large parasitic capacitance. This often causes the TSV 130 to have an observed capacitance that is significantly higher than the relatively low maximum pin capacitance specification.